Variable condenser



Dec. 17,A l929.` w. DUBILIER VARIABLE CONDENSER Filed Jan. 16. 1924 2Sheets-Sheet nucl/1 Foz Dec. 17, 1929. w. DUBILIER VARIABLE CONDENSERFiled Jan. 16. 1924 2 Sheets-Sheet Patented Der. 17, i929 UNITED STATESPATENT oFFic-E Y WILLIAM nonnina, or NEW Yoax, ir.v Y.,

` ABSIGNOB TO DUBILIB COB- POBATION, 'A CORPORATION 0F DELAWARE VARIABLEcoi'mENsEa- Applicatlon med January 18, 1924. Serial 111.680,54'.

My invention relates to condensers, and

more particularly to variable condensers.

Anobject of my invention 1s to provide a condenserin which thevariations in set' tin may be exceedingly minute. I

nother object of my invention is to provide a condenser in which the.parts `are so supported that the danger o f injury'through .carelessusage is almost entirely obviated.

necessary. This has beentrue for the reason that condensers of largeenough capacity to be practical, register a largel change 1n capacityfor a small cha-nge in setting.

through careless handling, the parts of variable condensers now incommon use are sub- Moreover,

ject to derangement or` displacement, and consequently to injury. l Y lIn my apparatus herein disclosed, I have rovided condenser elements,one,of which is iexible'and of spiral shape. The spiral shaped elementis deformed to cause it to be progressivelylaid on the other element ofy the condenser. VA relatively greatrlength of resilient element can beprogressively moved into and out' o-engagement withl the fixed condenserelement, with small change of lcapacity, since the spiral shape permitsa great length of movable element to be comprised in a. small condenser.The great length of the kfiexible movable element permits minutevariations to be made; change in capacity of 4 the device for any givenlength of movable yond its maximum values.-

velement brought` in contact with the fixed element vcan be made small.The ''exible spiral element of the condenser is spring Supa ported, thusobviating to a large degree possibilityl of injury to the condenserelements through attempts to adjust the condenser beand minimum capacityFigure 1 is a longitudinal sectional view i ltaken through the axis ofthe operatingfshaft on the line 1--1 of Fig. 2, looking in the directionof the arrows; Fig. 2 is abottom plan view of the condenser, artly insection, taken on the line 2-2 of 1g. 1, looking in the direction of thearrows;

Fig. is a top plan view of my condenser v partly in section, taken' onthe line 3'3 of.

ig. 1, looking in the direction of the arrows; i t

Fig. 4 is .a lon itudinal sectional view of a modification o mycondenser, such view.

- correspondin `to the view of my preferred form of con enser shown inFig. 1.

Referring tothe drawings for a detailed description,y I have shown acondenser casing l.

orsupport 1 ofbakeliteforsome other suitable-insulating material, havinga downwardly. depending annularlip 2, and provided with ian upstandingcentrally .located protuberance 3. Against the upper inner wall 4 of thecasing 1 is placed an annular strip of metal foil 5, :which comprisesthe metallic ortion of a fixed condenser element.'y The oil 5 isprovided with a tab 6 which extends beyond thel periphery of the foil.Fitting over the tab 6 is a metallic holding washer v 7 and passingthroughthe metallic holding washer 7 and the casing 1 is a binding ost jA8. A screw-threaded portion 9 of the bin in post extending above thecasing l'has fitte thereover a washer 11', and over thewasher 11 a bolt12. .The binding post 8 comprises one ofl the terminals of thecondenser, and connection to that terminal may be made by lacing "a wirebetween-the washer 11 and) the nut 12'and tightening the nut 12. Thefoil 5 isf. preferably fastenedwithin a slight depression'13in the upperwall 4 of the casing 1, and the center of the foil 5 is cut away to leava round aperture therein, as indicated at 1 Fastened over the foil 5 bisan insulatingv sheet 15, preferably of mica, which is attached to thefoil 5 by some suitable adhesive. The

i mica strip 15 is cut away, as indicated at 16, lto permit the holdingwasher 7 to make electrical contact with the foil 5. 10

On the interior of the casing there is affixed at one end a spiralresilient metallic element 22. The end 23 at the outer diameterof this sirai element 22 is held in position by the binding post 17, and thespiral element 22 is intentioned away from the fixed element.

Passing through an apertureI 24 formed in the center of the spiral,approximately at the inner end 25, is a reciprocablel shaft 26. Theshaft 26 has fitted over it a -supporting washer 27 prevented fromdownward movement on the shaft by means of av cotter pin 28. A helicalspring 29 is mounted over the shaft- 26, and has its lower end 31 keyedinto an aperture 32 in the holding washer 27.

The upper end 33 of the spring 29 is keyed in a hole 34 provided in theend 25 of the. b

resilient metallic movable element 22. The reciprocable shaft 26 passesupward through the protruding portion 3 of the casing 1,

through an aperture 35 formed in that portion of the casing.Screw-threads 36 are formed on shaft 26, which are adapted to enage withan internally screw-threaded coltr 37, keyed and firmly held within aninterior aperture 38, formed in an operating knob 39 of bakelite, orsome other insulating material.

The upper side of the protruding member 3 formed on the casing 1is'formed with a horizontally extending annular flange 41-.

Resting on the u per surface of the member 3 is a friction was er 42which is downwardly depressed, as indicated at 43, into a pocket iformed on the upper surface of the protrudven ing member 3. Thisprevents the friction washer 42 from rotating. The friction washer 42 isprovided with a tab 44 which projects into a longitudinal slot 45 formedin the reci rocable shaft 26. The friction washer 42, tiirough the tab44, prevents rot-ation of the reciprocable shaft 26. To hold theoperating knob 39 in position, there is provided a U-shaped holdingcollar 46 which surrounds the annular flange 47 formed on the bottom ofthe operating knob 39. The collar is a split collar, and is deformed tofit over the fianges, after which the spring of the metal draws it inplace, where it is held bv a bolt 48 and nut 49 that pass i through theends 50.` The holding collar 46 does not fit so tightly as to preventfree rotation of the operating knob 39, whose rotation electhecondenserbeyond its carries with it the internally threaded member 37, adapted toturn with the operating knob 39.

Rotation of the operating knob 39 causes the reciprocable shaft 26either to-be drawn up into the knob, or pushed downwardly, del pendingon the direction of rotation. The

shaft 26 is prevented from rotation by means of the tab 44 formed on thefriction washer 42. The movement of the shaft carries with it the spring29 )and consequently the free end .of the spiral member 22. The spiralmember 22 is subjected to a picking up and laying down action, on thefixed element of the condenser, comprising the foil 5 covered by theinsulating mica sheet 15.

The capacity of the condenser may be sub- .ting of delicate adjustmentis of peculiar advantage in radio communication. Moreover, y reason ofthe spring connections between the reciprocable shaft 26, and` themovable member of the condenser, attempts to adjust maximum and minimumvalues will accomplish no harm, since the sprin'gr connections preventinjury to the delicate parts.

Referring to Fig. 4, I have shown a different modification of myinvention embod ing the same principle of operation. In the ferm shownin Fig. 4, the spiral member 22 is in inverse position, and is adaptedto be laid down upon the fixed member beginning at its small diameterand progressing to its lar er diameter. In this form of device, thereciprocable shaft 26 is provided at its lower end with a screw-threadedportion 51. Threaded over the shaft 26 isa supporting plate 52,preferably of bakelite, or some other suitable insulating material. Theplate 52 rests on an annular flange 53 formed on a hollowed bolt member54, whose interior threads engage with the threads 51 of thereciprocable shaft 26. In the position of maximum capacity,when theplate 52 compresses all of the spiral 22 against the fixed element ofthe condenser, the compressed spring 29 is housed in the hollowed boltmember 54. The end 25 of the spiral resilient movable member 22 isfastened by means of screws 55 against a conductor str1p 56 positionedagainst the center of the upper wall 4 of the casing 1. The conductorstrip 56 passes upwardly and outwardly through the aperture 57 formed inthe casing 1, and then along the casing. The bindmovable member may bemade throu i h binding post 17 by loosening the nut 21 an clamp- -mentisgiven a slight offset, as indicated at' 58, to prevent injury to themica or the foil of the fixed condenser element in the operation of thecondenser. This offset insures that the mica and foil will not besubjected to a pinchin action at their edges. If such pinching actionshould take place, however, there would be slight danger ofshort-circuit ing, by reason of the fact that in all ofA these forms ofcondenser, the fixed element is composed of a strip of foilwhose innerand outer eldges are overlapped by the insulating mica s eet. Y

The operation of the form of condenser `-shown in Fig. 4 is quiteAsimilar to my preferred form illustrated in Figs. 1 to 3 inclu sive.-In the form of condenser shown in Fig. 4, the laying down operationbegins at the'small diameter of Ithe spiral, in other words, near thecenter, and is progressively continued to the larger or outer diameterof the spiral.

While I have shown and described the preferred embodiment of myinvention, I wish it to be understoodthat I do not confine my self tothe precise details of construction herein set forth, by way ofillustration, as it is apparent that many changes and variations may bemade therein, b those skilled in the art, without departing rom thespirit of the invention, or exceeding the scope of the appended claims.A

I claim 1. A variable condenser comprising, a support, a fixed elementcarried by the support, a rotatable screw-threaded member, a spiralmovable element, 4a screw-threaded shaft with a channel therein whosethreads engage the threads of the screw-threaded-member, a

washer fixed to the support between theI screw-threaded member andthesupport, a

"lug on the washer fittinginto the channel of the shaft, and meansoperated by the reciprol cation of the shaft to progressively press thespiral element against the fixed element.

2. A variable condenser comprising a fixed -`elementanda movable elementseparated by insulation, the movable element having-the form of a flatspiral, and means for deforming said spiral element to vary the capacityof the condenser. 1

3. A variable condenser comprising a support, a fixed element attachedthereto, a resilient element in the form of a fiat spiral fas-l tened atone end to said support and having its free end spaced from the fixedelement, dielectric material between said elements, and

means engaging the free end of the spiral element to cause the sametovapproach and recede from said fixed element in order to vary thecapacity of the condenser. v

4. Al varlable condenser comprising a fixed element, a movable flexibleelement in the form of a spiral having a plurality'of convolutions, saidspiral having a fixed end and a free end,'dielectric material betweensaid elements, and means including a 'spring engag-v ing the free end ofsaid spi-ral for causing its surface to progressively approach andrecede from the fixed element.

5. A variable condenser comprising'a fixed element, a resilient elementinthe form of a spiral having a plurality of convolutions, insulationbetween said elements, and a screw cooperating with the spiral elementto cause it to approach and recede from the fixed element in order tovary the capacity of the condenser. i

6. A variable condenser comprising a support, a fixed element attachedthereto, a resilient element in the form of a -flat spiral fastened atits larger end to saidA support and having its smaller end spaced fromthe fixed element, dielectric material between said elements, and meansengaging the smaller end of said spiral to cause its surface toprogressively approach and recede from the fixed element.

In testimony whereof I aflix my signature. WILLIAM DUBILIER.

